STEPHENVILLE, Texas (AP) — A Texas sheriff says the man charged with killing a former Navy SEAL and his friend was shocked with a stun gun and restrained in his jail cell after becoming aggressive.

Erath County Sheriff Tommy Bryant says 25-year-old Eddie Ray Routh is on suicide watch.

Bryant says Routh also appeared ready to assault jailers Sunday night when they entered Routh’s solitary confinement cell because he refused to return his food tray. Bryant says after using the stun gun once, jailers put Routh in a chair that restrains his arms and legs.

Routh is charged with fatally shooting Chris Kyle, author of the best-selling book “American Sniper,” and his friend Chad Littlefield at a shooting range Saturday.

The sheriff says Routh has an attorney but hasn’t met with him.

Watch these ABC News reports about Chris Kyle: