A man charged last month with child sexual assault is now charged with sexually assaulting a second child.

Christian S. Klapper, 23, of 1936 N. Highway 104, Albany, was charged Aug. 7 in Rock County Court with first-degree sexual assault of a child under age 13.

He was charged Aug. 23 with two counts of possession of child pornography.

On Thursday, he was charged with sexually assaulting a second boy under age 13.

Both boys knew Klapper, according to the complaint.

The criminal complaint in the earlier case states that a young boy told a Rock County sheriff’s detective Klapper sexually assaulted him at Klapper’s home, and a witness saw the assault.

The allegation by the first child led to a search warrant being executed at Klapper’s home, where a laptop was found. The laptop’s hard drive included two deleted videos showing boys engaged in sex acts, according to the criminal complaint.

The complaint says the second assault occurred in early July when Klapper and the boy were watching a movie at Klapper’s home and the boy fell asleep, only to awake to find Klapper assaulting him.

The search warrant affidavit quotes information from a relative of the boys who told investigators Klapper would insist the boys he was babysitting drink smoothies, and one boy said he would fall asleep and wake to find his clothing disheveled.

The relative said the boy’s urine tested positive for THC, the psychoactive ingredient in marijuana, with a home test kit.

The relative told investigators Klapper had texted other family members, offering to babysit, but everyone declined because they had heard about the investigation, according to the document.

Klapper has pleaded not guilty in the first two cases. He was being held at the Rock County Jail on two cash bonds totaling $15,000. On Thursday, a cash bond of $5,000 was added.

Capt. Todd Christiansen of the sheriff’s office detective bureau told The Gazette on Wednesday that Klapper is the subject of an ongoing investigation.