The self-explanatory phrase to come (also to be) down on someone like a ton of bricks means:
– to attack or punish someone with great vigour;
– to reprimand someone severely.

A variant of this phrase occurs, for example, in the following from Crossword editor’s update, published in The Guardian (London and Manchester, England) of Tuesday 21^st March 2017:

The long arm of coincidence …
… or things that just happen
Crossword coincidences have been on my mind this last month. Most of you will know the story of how eight top secret code words appeared as solutions in the Daily Telegraph crossword in the weeks immediately before the Normandy D-Day landings on 6 June 1944. These were Juno, Gold and Sword (the three British and Canadian assault beaches) and Omaha and Utah (the two American targets). On 27 May, Overlord (code for the entire operation) appeared, followed on 30 May by Mulberry (the floating harbours) and on 1 June Neptune (code for the naval assault operation).
The puzzles had been set by Leonard Dawe, headmaster of a school evacuated to Effingham in Surrey. Less well known is the earlier story that, on the day before the disastrous Dieppe raid in August 1942, involving 5,000 Canadian, 1,000 British and 50 American troops, most of whom were immediately killed or captured, Dieppe appeared as a Telegraph solution. In both cases MI5 descended like a ton of bricks, but finally chose to conclude that these were just ‘coincidences’.

The earliest occurrences that I have found of the phrase to come (also to be) down on someone like a ton of bricks are as follows, in chronological order:

1-: From Our Albany Letter, dated Friday 7^th February 1862, by a person signing themself ‘The Captain’, published in The New York Atlas (New York City, New York, USA) of Sunday 9^th February 1862:

McLeod presented a petition here to-day, (Friday,) signed by Hon. Daniel R. Jaques and Judge Bull, in relation to the Hackley contract, the confirmation of railroad grants, the Gansevoort property, etc. It is sweet-scented I can assure you, and comes down on the bold Fernando, and the celebrated “Ring” of the Aldermen, like a ton of bricks, also slashes at Mat Green and his sinecure position of Inspector of Railroads. Something is going to be done, and the wicked are to be punished.

2-: From a correspondence from London, dated Saturday 23^rd May 1863, published in the Otago Daily Times (Dunedin, Otago, New Zealand) of Friday 24^th July 1863:

Gladstone’s budget on being pulled to pieces is not so rosy after all, and he has had to eat the leek financial more than once—he tried it on to tax Charity funds and West End Clubs; the Charities would have yielded a quarter of a million yearly; but […] in debate our champion Chancellor was floored. That suit settled, Clubs were trumps, and this was an awful game. The tax itself would only produce a couple of thousand, and as it was proposed to enforce a license which would level those aristocratic gambling shops with vulgar tap-houses, you may believe the Pall Mall clubites were down up n upon him like a ton of bricks—rumor says the classical innovator was once upon a time black-balled at the Carlton, and this was his Roland for their Oliver; any way rhetoric availed him nought, and Gladstone ate another leek.

3 & 4-: In each of the following two texts, the phrase like a ton of bricks refers to an actual physical attack:

3-: From Widder Spriggins’ Daughter, a poem published in the Daily Evening Herald (Stockton, California, USA) of Tuesday 26^th September 1871:

An old rampageous sheep
Who had been feeding near, sir,
Squared off, and like a ton of bricks
He took me with his head, sir;
I landed in a pond, chuck full
Of frogs and filthy water.

4-: From The Corvallis Gazette (Corvallis, Oregon, USA) of Saturday 18^th January 1873:

He Whipped Him.—A lad narrating a street fight in which he had been engaged, said:
“I’ll tell you how it was. You see, Bill and me went down to the dock to fish and I felt in my pocket and found my knife and it was gone, and I said to Bill, you stole my knife, and he said I was another, […] and I said he darsent take it up; but he did you bet. You never—well, you never did, then I got up again and said he couldn’t do it again, and he tried to but he didn’t and I grabbed him and throwed him down on me like a ton of bricks, and I tell you it beat all; and so did he.

5-: From a letter to the Editor, by Mr. Smith, “a working man on a station”, published in the Hamilton Spectator (Hamilton, Victoria, Australia) of Saturday 28^th June 1873—in the following, Mrs. Wonderful is talking about her mother, Mrs. Scarr, and of Mr. Nearkin, “a storekeeper in the neighbouring township”:

“When she went to get the land, Mr. Nearkin called and said she should have any money she wanted.” “Very kind,” says I; and I thought to myself he never said that same to me—in fact, if I owed him over a note, he was down on me like a ton of bricks.

6-: From a correspondence from London, dated Saturday 10^th July 1875, published in the South Wales Daily News (Cardiff, Glamorgan, Wales) of Monday 12^th July 1875:

Everybody is laughing this morning at the debate in the House of Lords last night. It was about the Irish peerage. Lord Stanhope thought it inexpedient that the Queen should make any more Irish peers. He moved a resolution to the effect that an humble address be presented to her Majesty, praying that she would be pleased to relinquish her prerogative and power of creating further Peers of Ireland, and that the concurrence of the House of Commons be desired in such address. One would have expected him to be very exact, for he is an historian. […] But he used a wrong word. The Queen has no “prerogative” to create Irish peers. Whatever right she has is derived from statute law. This was a fine error for the Lord Chancellor. It gave him a splendid opportunity, and he was down on Lord Stanhope “like a ton of bricks.” For more than an hour he argued his point. The learning displayed was positively oppressive. The endeavour to be logical was bewildering; and the desire to be exhaustive was manifested so strongly as to be wearisome.

7-: From the account of a meeting of the shareholders of the Great Western railway, published in Herapath’s Railway and Commercial Journal (London, England) of Saturday 10^th March 1877:

It has long been a subject of remark that wherever the Midland and Great Western are found in competition the former wins popularity. The more enlightened and active business management of the Midland may be the cause of the preference alluded to, but we perceive that some Great Western Proprietors assigned at the meeting another cause for that Company’s want of success, namely, mismanagement. Mr. Mirehouse, resident in the neighbourhood of Bristol, was “down upon” Great Western management “like a ton of bricks,” if we may be forgiven the slang. He “could only tell them that Bristol traders had every possible thing sent down by the Midland because they could not stand the delay caused by the Great Western railway.”