The Monroe County Sheriff’s Office is conducting an internal investigation into how a deputy’s assault rifle, two pistols and tactical gear were stolen from his cruiser earlier this week.

On Wednesday, deputies arrested 17-year-old Big Pine Key teen Kalvin Cowger in connection with the theft, and Sgt. Ken Fricke’s M4 carbine assault rifle, tactical gear and ammunition for the rifle were recovered. Still missing, however, are Fricke’s department-issued .40 caliber Glock and his personal sidearm, a .45 caliber Glock.

The weapons were stolen some time between last Sunday and Tuesday morning. Fricke told detectives he heard his dogs bark between 2 and 2:45 a.m. Tuesday morning, but he did not get out of bed to investigate. He said he last saw his handgun Sunday evening.

Fricke is a member of the agency’s Special Weapons and Tactics Team. The M4 rifle recovered Wednesday is a carbine version of the M16 assault rifle. The U.S. Army is switching to the shorter M4 as its standard issue combat rifle.

Crime scene investigators said they can’t determine how access was gained to the vehicle. Police canvassed the neighborhood to see if anyone saw or heard anything.

When reached for comment on whether he left his patrol car unlocked, Fricke told KeysNet that he could not comment because the matter is still an active investigation.

Deputy Becky Herrin, a sheriff’s office spokeswoman, said she could not comment on what she called an “internal investigation.”

According to the sheriffs office’s general orders, off-duty deputies cannot store firearms in their department-issued vehicles “unless the firearm is secured with a locking device/container mounted to the inside of the vehicle.”

Also, the general orders state off-duty deputies “shall not store issued laptop computers, ballistic vests and any clothing with police identifiers in their issued vehicles.”

A call to Crime Stoppers led to Cowger’s arrest, according to police, who said they interviewed a witness who called in to report that Cowger showed her a bag with the stolen items inside. The witness told police the suspect was going to trade the guns for drugs, Herrin said.

Detective David Brummer went to the home of a Big Pine Key man who was identified by the witness. Police say the man was cooperative and let the detective search his house. Inside, Brummer found the missing M4 assault rifle and the SWAT gear. The man said he received the items from Cowger, but said he didn’t know the items were stolen.

Another witness told police he saw Cowger on Monday at about 5 p.m. and said Cowger offered to sell him two handguns, Herrin said. He told cops he refused to buy the handguns, which are still missing.

Detective Brummer set up an interview Wednesday with Cowger, who denied knowing anything about the burglary or the stolen items, police said. Cowger was arrested and is facing charges of possession of stolen property and theft. The investigation continues, police said, and more charges or arrests may be pending.

State law prohibits the release of a law enforcement officer’s home address, so the exact location of the crime is being withheld on police reports made public.

Anyone with information is asked to report it at 305-289-2351. Callers who wish to remain anonymous can contact Crime Stoppers of the Florida Keys toll-free at 800-346-TIPS or submit online at: www.tipsubmit.com