Credit: Kevin Mazur/

The self-professed warlock is on the warpath...again.

This time, second wife Denise Richards is caught in Charlie Sheen's cross hairs.

What set him off? A source tells the new issue of Us Weekly (on stands now) that Richards, 40, angered her ex by intentionally putting distance between Sheen, 45, and daughters Sam, 7, and Lola, 5, as he continues to meltdown in the public eye.

"He wanted to pose in a picture with the girls a few days ago," says the insider. "And when Denise refused, he threatened her with physical harm." (A source close to Sheen denies the incident.)

Richards was so troubled by his erratic behavior, in fact, she banned the former Two and a Half Men star from Sam's 7th birthday party on March 13 at L.A.'s Monarch Gymnastics center. "Denise is constantly trying to shield them from their dad's problems," says another source. "But it was becoming harder."

For even more on Sheen's frightening antics -- machete wielding tantrums, alleged assaults -- check out the new issue of Us Weekly, on sale now!