Story highlights The shooting victim had lost an arm and a leg in a train accident

Police say man was "advancing" toward a cornered officer

Another police officer warned the man to stop and drop whatever he held in his hand

Reports say officer had been involved in another police shooting

Houston police shot to death a double amputee in a wheelchair who they said was trying to stab an officer with a pen.

The man, Brian Claunch, was shot in the head Saturday morning after two police officers arrived at a group home for the mentally ill. The officers were responding to a report that Claunch -- a reported schizophrenic who lost an arm and a leg in a train accident -- was acting aggressively.

His caretaker had refused to give him a cigarette and a soda, according to police and the facility owner.

Police said Claunch was clutching an object as he advanced on one of the police officers.

"The officers made verbal commands for the suspect to drop whatever he had in his hand, to stay still and to speak with the officers, but the suspect continued to make threats," Jodi Silva, a police spokeswoman, told CNN affiliate KTRK in Houston

Brian Claunch suffered from schizophrenia and a bipolar disorder, said the owner of a group home where he stayed.

Claunch trapped one officer with his wheelchair in the corner of a room "where he couldn't get out," said a Houston police department representative who declined to be identified.

As he advanced toward the officers, Claunch was "refusing to show his hands," the representative said.

The object turned out to be a pen, which Claunch attempted to use to stab the cornered officer, according to police accounts reported in the media, including by KTRK.

The other officer, Matt Marin, was "in fear of the safety of his partner and the safety of himself," Silva said. Marin then fired his "duty weapon, striking the suspect," Silva said.

On Sunday, the unidentified police representative offered more details, saying that, unlike his partner, Marin was not cornered at the time he opened fire.

Claunch was shot once and he died at the scene, according to investigators. Marin has been placed on administrative leave per department policy, police said.

The incident was the second shooting involving Marin. In October 2009, he shot and killed a knife-wielding man who stabbed his girlfriend and a neighbor, according to published reports at the time. Marin joined the Houston Police Department in 2007.

Claunch, who was in his 40s, had been at the Healing Hands group home for 18 months, owner John Garcia told KTRK.

Houston police have not released the identity of the man, though Garcia identified him as Claunch.

Garcia told the Houston Chronicle that Claunch liked to "doodle," which may explain why he was holding a pen.

Garcia reportedly said he had given Claunch a black felt pen for drawing. Garcia told the Chronicle he did not know if that was the pen Claunch was clutching when he was shot.

Garcia said Claunch suffered from schizophrenia and a bipolar disorder.

"He had a temper. He could fly off once in awhile," he told CNN affiliate KHOU

Claunch was capable of flying into outrage and making people in the house feel threatened, even though he was confined to a wheelchair, Garcia said.

"Emotionally disturbed individuals, when threatened, are going to react, in most instances, excessively," Dr. Ed Reitman, a clinical psychologist, told KTRK.

"This was an incident that didn't have to take place if the individual -- a police officer -- had been trained in dealing with emotionally disturbed individuals."

The Houston Police Department has officers trained to deal with mentally ill people, though the department would not say whether Marin received training, according to KTRK.