* Investigators still seeking motive for shootings
* Gunman had history of mental illness (Corrects the number of wounded to 7, from 8, in first paragraph to conform with latest casualty toll)
By Steve Keegan
CARSON CITY, Nev, Sept 6 (Reuters) - A man with an assault rifle opened fire at a pancake house in Nevada's capital on Tuesday, killing three National Guard soldiers and a civilian and wounding seven others before killing himself, authorities said.
The gunman, in what investigators said appeared to be a random burst of violence by a grocery worker with a history of mental illness, opened fire at a group of uniformed Army National Guard troops as they ate breakfast.
Besides the three Guard soldiers -- two men and a woman -- who were shot to death at the Carson City IHOP restaurant, two of the wounded were also active-duty Guard members. A civilian woman in the line of fire between the gunman and soldiers was killed as well.
Carson City Sheriff Kenneth Furlong told reporters that the fact that five of the 11 people shot were military was a "cause for concern".
But he and other officials said there was no sign that the gunman, a Mexican-born U.S. citizen, knew anyone at the restaurant or had singled out members of the military before he entered the IHOP.
"At this time, the investigation has not shown any links to terrorism or militant groups," FBI special agent Patrick Turner said in a statement. "We do not believe the National Guard soldiers were targeted specifically, however, that is still under investigation."
At least one of the wounded was shot outside the restaurant, but the sequence of events at the chaotic crime scene was still being unraveled, Furlong said.
Several of the wounded were undergoing surgery at two local hospitals, but details of their conditions were not immediately available. Furlong said three of those wounded did not appear to have sustained life-threatening injuries.
The suspect, identified as Eduardo Sencion, 32, initially survived his self-inflicted gunshot wound but later died at an area hospital, police said.
NO WRITINGS BY GUNMAN
FBI special agent Mike West said investigators had yet to find any Internet postings or other writings left by the gunman, who authorities said worked for his family-run grocery business in South Lake Tahoe, California.
Sencion has no prior criminal record, but "his family has indicated that he has a history of mental illness," Furlong said.
In addition to the weapon used in the shooting, described as a variant of an AK-47 assault rifle, Furlong said a second rifle and a pistol were found in the gunman's vehicle.
The state capitol, legislature and Supreme Court buildings were locked down for about an hour shortly after the shooting as a precaution.
Nevada Governor Brian Sandoval ordered flags flown at half-staff until Friday at dusk in honor of the two National Guardsmen who were killed.
Sheriff's Commander Jack Freer said officers responding to reports of a man with a gun at about 9 a.m. local time found victims with gunshot wounds in the parking lot of the restaurant. More victims were discovered inside, he said.
"The suspect was found down with a self-inflicted gunshot wound," Freer said.
Ralph Swagler, owner of the Locals Barbecue shop in the same strip mall as the IHOP, told the Reno Gazette-Journal newspaper that he saw a man wearing a red shirt and black shorts pull up outside the IHOP in a blue minivan.
Swagler said the man, armed with a rifle, shot a person on a motorcycle, then walked inside the IHOP and started shooting.
Swagler said the man spent several minutes there, then walked back outside into the parking lot and began firing into the Locals Barbecue and an H&R Block in the strip mall.
Fran Hunter, 64, who works at Sierra Le Bone, a pet shop near the IHOP, was having breakfast across the street when the shooting occurred, and was so shaken she returned to her own business and locked the doors.
"You read about this happening in big cities, but not in our little town," she told Reuters. (Additional reporting by Steve Gorman, Dan Whitcomb and Timothy Pratt, Cynthia Johnston and Alex Dobuzinskis; Writing by Dan Whitcomb and Steve Gorman; Editing by Jerry Norton and Cynthia Johnston)