US federal agents believe the slain suspect in a deadly attack on worshippers at a Sikh temple in Wisconsin had ties to white supremacist groups, a senior investigator said.
Special Agent Teresa Carlson, head of the Federal Bureau of Investigation's Milwaukee field office, confirmed that 40-year-old suspect Wade Michael Page is the subject of a "domestic terrorism" probe following Sunday's massacre.
"We are looking at ties to white supremacist groups," Carlson told a news conference a day after Sunday's shooting, in which six people attending a service at a suburban Milwaukee temple were gunned down.
"We did not have an active investigation on him before yesterday," she said. "No law enforcement agency had any reason to believe he was plotting anything.
"We are working on it as a possible domestic terrorism case," she added. "The definition of domestic terrorism is the use of violence for social or political gain. That's obviously what we are looking at."
Investigators also released a picture of a second man -- who was white, with short brown hair and a muscular build -- who they described as a "person of interest" and who raised suspicions when he joined crowds viewing the police cordon outside the temple on Sunday.
They urged members of the public to come forward with any information on Page, the person of interest or any other details which may help their investigation.
"We don't have any reason to believe there was anyone else associated with this shooting," Carlson said.
"We are continuing to work and if there is anybody we will identify them."
Carlson said the FBI was always on the alert for possible copy cat attacks after such an incident, but noted that investigators had no specific reason to fear that any further violence is being planned.
Investigators are also not aware of any connection Page may have had to the temple, which had not received any threats prior to the incident.
"The FBI is going to do everything in our power to fully and efficiently investigate this case and do everything to prevent this from ever happening again," she added.
Officials said the firearm retrieved at the scene of the shooting was a 9mm handgun that had been purchased legally and that the shooter had brought several magazines with which to reload the weapon.
Police evacuated several blocks of neighboring Cudahy as they prepared to search Page's home Sunday but did not find any boobytraps.
Carlson declined to say what type of evidence was discovered or if Page had left a note.