Police in Menifee arrested a 17-year-old Heritage High School student after they said he sent threatening messages to other students and found him with what is believed to be a “ghost gun.”

The student was arrested early on Saturday as he was returning to his home, police said in a statement. When they searched the teen, officers found a pair of brass knuckles and the gun on him.

Police went to the student’s home after they got a call earlier that morning about the threatening messages, which he allegedly sent through social media.

The messages did not specifically target Heritage High or other students, but were apparently threatening enough that others who saw them on social media called police.

The student was not publicly identified. Police said he did not appear to have a previous criminal record. He was booked in Riverside County Juvenile Hall.

He has not been charged yet, but could face charges for criminal threats and possessing the brass knuckles and the unregistered gun.

Captain Dave Gutierrez said the handgun did not have a serial number on it that would make it traceable by police, which is what earned the weapons the “ghost guns” moniker.

The gun appeared to have been built out of a kit. Such kits are available online and allow anyone to build a gun from pieces bought separately.

California law enforcement leaders have become increasingly concerned about weapons built in this way that are appearing more frequently at crime scenes and in the hands of people who shouldn’t have them.

It’s not clear how the 17-year-old got the gun.

“At this point we don’t know whether or not he bought the stuff (to assemble the gun) or not,” Gutierrez said.

There was no information Sunday about when the student would appear in court.