THE sister of a veteran Texas prosecutor who blew his brains out as he was about to be busted in an underage-sex sting set up by “Dateline” is slapping NBC with a $100 million suit.

Louis “Bill” Conradt grabbed a gun and shot himself as he spotted cops, reporter Chris Hansen and a camera crew from the popular “To Catch a Predator” segment outside his home on Nov. 5, 2006, according to a notice of claim sent to NBC yesterday.

The suit will be filed Monday in Manhattan Federal Court on behalf of his estate, said Patricia Conradt’s lawyer, Bruce Baron.

“NBC was responsible for his death. They conducted their sting operation and intentionally and with negligence sensationalized the situation,” Baron said.

“It brought it to the point that he died of a self inflicted gun shot wound.”

The 56-year-old prosecutor, a highly praised 20-year-law enforcement veteran, allegedly went online to solicit sex from a 13-year-old boy.

Hansen and a “Dateline” crew tagged along with cops to the prosecutor’s home to capture the arrest.

NBC said if a suit is filed, “we will defend ourselves vigorously, as we believe the claims are completely without merit.”