INDIANAPOLIS -- A former Marion County sheriff's deputy was arrested in Indianapolis last week on suspicion of sending threatening messages to his ex-girlfriend, who lives in southwestern Ohio.

Police also said Christian Keen -- who was a member of the department's SWAT team -- possessed firearms in violation of a protective order that his former wife had against him.

Indianapolis and Westchester, Ohio, police on Friday found more than 50 guns during a search of Keen's home on Indianapolis' southwest side, authorities said. According to police, Keen told investigators he was a member of Blackwater USA, which provides private security in Iraq.

Authorities said they believe Keen used a phone, text messages and a computer to threaten his ex-girlfriend, who lives in Westchester, during a period of more than a month. According to a police report, the ex-girlfriend kicked Keen out of her car last month in Kent, Ohio, after they took a trip together.

"We look at these very seriously, any of these threats that are made, and here's an individual, I think ... that is capable of carrying this out," Westchester police Sgt. Steve Oakes told 6News' Jack Rinehart on Monday.

Keen was arrested on felony charges of stalking and invasion of privacy. He was extradited to Westchester and is expected to appear in a Butler County, Ohio, court on Tuesday.

Keen received a medical discharge from the Marion County Sheriff's Department last year after injuring his back, Rinehart reported.