The laid-off designer who executed a former coworker outside the Empire State Building spent two years blaming his victim for his financial woes — but he finally snapped when he learned he was being evicted from his Upper East Side apartment, The Post has learned.

“This was the final straw that pushed him over the edge,” a police source said yesterday. “He was blaming the victim for being out of work, having no money and now having no apartment.”

Shooter Jeffrey Johnson—who served in the Coast Guard as a petty officer second class in the 1970s — brooded over his dismissal from Hazan Import at 10 W. 33rd St., where he worked for six years.

He was laid off simply because “business was bad,” a Hazan employee said.

But for Johnson, the blame rested on salesman Steven Ercolino, who the shooter thought was not doing enough to push the products he designed, a source said.

Even before his layoff, Johnson and Ercolino were already on poor terms.

“Johnson filed a complaint against Ercolino saying he had a confrontation with him in the lobby of the building,” Police Commissioner Ray Kelly said yesterday.

“Ercolino filed a complaint saying he was threatened by Johnson and he possibly threatened to kill him.”

His breaking point came when his landlord threatened the man with eviction.

Johnson was no longer able to make rent on the onebedroom co-op he had rented on East 82nd Street for about four years, a police source said.

Johnson — a bird-watcher who just last Wednesday blogged about his hobby in Central Park—blamed that on Ercolino, and on Friday exacted his revenge.

Wearing a full suit, Johnson lay in wait behind a truck outside the 33rd Street building until Ercolino arrived around 9 a.m.

He shot his defenseless victim in the head and then pumped another four bullets into his body.

The killer then calmly turned the corner to Fifth Avenue, where he drew his gun on a pair of NYPD cops on anti-terror patrol.

The officers fired 16 times, killing him and wounding