ORLANDO, Fla. — A lone gunman returned with a semi-automatic pistol to the Orlando awning factory where he was fired in April and methodically killed five people today, then killed himself at the sound of an approaching siren, the Orange County sheriff said.

The shooter was identified as John Robert Neumann Jr., a 45-year-old Army veteran who lived alone and did not appear to be a member of any type of subversive or terrorist organization.

The shooting began at about 8 a.m. after Neuman slipped through a rear door into the cavernous factory, an area that stretches across more than two football fields where awnings are stitched together for recreational vehicles.

“My experience tells me that this individual made deliberate thought to do what he did today. He had a plan of action,” the sheriff said. “We have information that at least one of (the victims), he had a negative relationship with. He was certainly singling out the individuals he shot.”

“Most of the victims were shot in the head; some were shot multiple times,” the sheriff said.