Pennsylvania state police acted recklessly when troopers used a bulldozer to pursue a 51-year-old Grateful Dead fan who had been caught growing marijuana on public land, killing him when he wound up under the machine’s treads, according to a civil rights lawsuit filed on Monday.

Greg Longenecker’s family said police had no business chasing him with a dangerous piece of machinery, especially over a few pot plants he was cultivating for personal use.

His death last July, in a rural area about 75 miles outside Philadelphia, also provoked outrage from a marijuana advocacy group.

“They killed a beautiful human being, a caring, loving man,” said Longenecker’s uncle, Mike Carpenter, who is named as a plaintiff in the federal suit. “He’ll never be able to share his life with us, or us with him, again. For no reason. He wasn’t hurting anyone.”

Mike Carpenter, uncle of Greg Longenecker, walks the field where Longenecker was killed by a bulldozer in 2018, in Bernville, Pennsylvania. Photograph: Jacqueline Larma/AP

State police declined comment. A prosecutor who investigated Longenecker’s death concluded that troopers acted reasonably.

The chase developed as Longenecker – a short-order cook and avid vegetable gardener – and his friend, David B Light, tended 10 marijuana plants in a small clearing on state game lands near Reading, Pennsylvania. A Pennsylvania game commission worker, operating a bulldozer in the area, spotted their car parked in a field where vehicles were not allowed and called police.

Light surrendered but Longenecker fled, disappearing into the thick vegetation. Police began a lengthy search. A helicopter spotted Longenecker in the underbrush, and the game commission worker, with a trooper aboard, used the bulldozer to blaze a trail in pursuit. The bulldozer was traveling no more than 1mph or 2mph, according to an official account.

How Longenecker got caught in the machine’s treads is hotly disputed. Authorities concluded he was high on methamphetamine, crawled under the back of the bulldozer in an attempt to elude capture, and was crushed to death when it made a left turn. Longenecker’s friends and family call that explanation ludicrous.

“That morning, Gregory was not high or under the influence. He was normal,” Light wrote in an affidavit obtained by the AP. “There is no way Gregory crawled underneath the back of the bulldozer. It is unthinkable and ridiculous that anyone would say he crawled underneath.”

Light, 55, pleaded guilty to misdemeanor drug charges and was accepted into a program for first-time offenders. He declined comment.

Longenecker’s family questioned why state police did not simply get a warrant for Longenecker and arrest him later, given they knew his identity and that his crime was relatively minor. An expert in police procedure agreed the state police overreacted.

“It’s outlandish. This is the craziest thing I’ve heard in years,” said Walter Signorelli, a lawyer and retired New York police commander who has overseen investigations into police pursuits. “It seems like they were more concerned with the chase than the danger to themselves and the public and the guy they’re chasing.”

The Berks county district attorney, John Adams – the prosecutor who determined that state police acted appropriately – said Longenecker put himself in jeopardy by fleeing from the authorities.

“His behavior was despicable,” Adams said. “They yelled to him, they asked him to surrender. He did not surrender.”

Longenecker would probably have faced probation over his marijuana plants, Adams said. He said the family would have been just as angry had troopers abandoned the search and it had turned out that Longenecker was injured and in need of medical attention.

“He’s in a pile of brush that is completely uninhabitable. Something could have happened to him. And if the state police would have picked up and left, then they would be pissed off: ‘Why didn’t the state police try to find him?’ So they were damned if they did or damned if they didn’t,” he said.

But at least one state police official has acknowledged the situation could have been handled differently. Carpenter, Longenecker’s uncle, said he met Sgt William Slaton from state police headquarters about a month after Longenecker’s death.

He said Slaton apologized, telling him that “for 10 plants, he would’ve sent everybody home because they already knew who he was, where he lived, where he worked. He would’ve sent everybody home and maybe picked him up a couple days later.”

A state police spokesman would not confirm or deny Carpenter’s account.

The suit, which was filed in Philadelphia, seeks damages against state police, the game commission and the individuals involved in the pursuit. A game commission spokesman declined comment.

“State police ran Gregory Longenecker over with a government-operated bulldozer and essentially turned him into human roadkill,” said the family’s lawyer, Jordan Strokovsky. “There will be a thorough investigation and a lot of questions will be answered, and ultimately, those who need to be held accountable will be held accountable.”