Once -smug killer DREW PETERSON cries like a baby as cops charging him with murder in disappearance of 4th wife, STACY, as law enforcement investigates multiple murders that may reveal Drew as a brazen serial killer – insiders.

AFTER being sen­tenced to 38 years in prison for the murder of his third wife, a once-cocky DREW PETERSON is so devastated that alarmed authorities have put him on a suicide watch, say insiders.

“Drew has broken down into an emotional heap,” a close source told The ENQUIRER. “He realizes he’s going to be in prison until he’s in his late 90s – and he cries like a baby. He got what amounts to a death sentence, and it’s shattered his cocky self-image. He’s even been talk­ing about killing himself.”

Former Bolingbrook, Ill., cop Peterson was sentenced on Feb. 21 for the murder of his third wife Kathleen Savio, 40, whose body was found in a bathtub in her home in March 2004. Originally, her death was ruled an accidental drowning, but her body was exhumed after Peterson’s fourth wife Stacy disappeared in late 2007.

A renewed investigation determined that Kathleen had been murdered, with the death scene disguised as a suicide.

Now Illinois pros­ecutors have slammed Peterson, 59, with even more bad news – they’re considering bringing new charges against him for murdering Stacy, whose body has not been found.

And the hits keep coming.

Investigators also believe Peterson could be a serial killer and are looking at other missing person cases, includ­ing that of Lisa Stebic, a mother of two who disappeared from her Plainfield, Ill., home in 2007. The cases under investigation go back 25 years, revealed Charles Pelkie, spokesman for Will County prosecutor James Glasgow.

All of this has apparently wiped the smirk off Peterson’s face. “Drew had been arrogant be­yond belief and never, ever believed there was any chance he would be convicted for Kathleen’s murder,” the source told The ENQUIRER. “He even planned to get married for a fifth time. But when he heard the judge hand down his sentence, it hit him like a sledgehammer and he fell into a dark de­pression. He felt the reality of the prison cell doors clanging shut behind him forever.”