Morongo Valley suspect arrested after threatening to 'kill many innocent civilians' in viral pro-ISIS Facebook post

A Morongo Valley resident was arrested Wednesday in connection with a pro-ISIS Facebook post that may have prompted the lockdown of an elementary school.

Robin Lee Rennaker, 21, was arrested following execution of a search warrant at his residence on the 49-700 block of Pioneer Drive, the San Bernardino County Sheriff's Department confirmed Thursday. During the search of Rennaker's residence, deputies found a sawed-off shotgun, ammunition, methamphetamine and drug paraphernalia.

Detectives also collected Rennaker's electronic devices for further investigation.

He was charged with possession of a sawed-off shotgun, criminal threats and probation violation. Rennaker was booked into the Morongo Basin jail and was being held with out bail.

Authorities said they were alerted to the Facebook post, which claimed ties to the Islamic State group and thretened to "kill innocent civilians," Tuesday night but were not able to make contact with Rennaker that evening and continued the investigation into Wednesday.

Morongo Valley Elementary School was placed on lockdown Wednesday morning after the social media threat.

The lockdown began when students arrived at the school and was lifted in the first hour, according to Morongo Unified School District Superintendent Tom Baumgarten.

Students and teachers gathered in the school as a precaution, Baumgarten said, since Morongo Valley is a small community.

At the time, concerned Morongo Valley citizens pointed to the Facebook post as possible reasoning for the lockdown.

The post had garnered more than 300 comments in 19 hours. Commenters said they have reported the post and expressed outrage at the threat.

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Tammy Stogner-Russell, a Morongo Valley resident, stayed home with her four kids today because of the Facebook post, which has had 75 shares since it was posted.

Stogner-Russell received a screenshot of the post Wednesday morning.

"Today was the first day of school my kids have missed in three years," Stogner-Russell said. "I kept them home because their lives are worth way more than (an attendance) trophy."

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Reporter Corinne S Kennedy contributed to this report