Scott Stapp ... Relatives Panic -- He's Out to Kill Obama (911 Tape)

Scott Stapp threatened to assassinate President Obama ... and his alarmed wife and sister-in-law made a desperate 911 call to stop him.

Scott had just gone AWOL from a mental facility late last month, when his sister-in-law told the 911 dispatcher he was cruising around his neighborhood, shirtless on a bicycle. She says the former Creed frontman claimed to be a CIA agent and his mission was to kill Obama.

Stapp claimed in a rambling video the IRS is trying to ruin his life because he's been trashing Obama.

Jaclyn Stapp, Scott's wife, joins the 40-minute 911 call, telling the dispatcher Scott had printed out 400 - 600 pages of CIA documents which he supposedly found online, put them in a book bag and took off on his bike.

The 2 women were pleading with the dispatcher to snare Scott and take him back to the psych ward.

As cops were dispatched, Scott placed his own 911 call, saying his wife had stolen his truck and that's why he was on a bike.

When cops arrived Scott told them Jaclyn had pilfered $6 mil from him, and when he confronted her she decided to get him locked up. In the end, police determined Scott did not show enough signs of mental instability to warrant a psych hold.

TMZ broke the story ... Jaclyn has filed legal docs trying to get Scott on a 60-day psych hold, claiming he was deep into various drugs, including coke, weed, PCP and amphetamines. Scott posted a video claiming he's drug free.