LONGMONT, Colo. -- Longmont police are praising the work of an alert mother who discovered that a man who was e-mailing her daughter is a convicted sex offender.

"My daughter came to me and told me she was talking to someone and it was starting to make her feel uncomfortable," the mom told 7NEWS.

She said her daughter met the man on MySpace.com.

When her daughter told her about the most recent e-mails, the mom swung into action. She started looking for phone numbers, and then on a hunch she decided to check the sex offender registry.

"When I saw his name and face pop up, that was the worst," she said.

She learned that Andrew S. Coslett, 30, had been sentenced to three years in the Department of Corrections for attempted sexual assault on a child in 2000.

"My head just started spinning. My gut hurt. I was so scared," the mom said.

That's when she called police.

"We looked into it," said Cmdr. Tim Lewis of the Longmont Police Department. "We found he had not registered, that he was working on the Internet, using the Internet and that was a violation of state law."

Other parents are praising what this mom did.

"I think that was a good thing to do," one parent said as she arrived at the library with her daughter and two friends.

Police are praising her work too.

"That mother was just fantastic in our eyes. We're very impressed with her activity and feel she prevented something much more tragic from happening," Lewis said.

Officers are investigating whether Coslett was communicating with any other children. His MySpace display name was"drewssiffer," but his account has been removed from MySpace.

In 2000, Coslett was arrested after he thought he was communicating with a 14-year-old girl. The girl was actually an undercover detective, so when Coslett arranged to meet up with her for sex, he was taken into custody by police.

He had previously been arrested for fraud, forgery, burglary and aggravated vehicle theft.

The mom told 7NEWS that she talked to her daughter about Coslett's background.

"When I showed her his photograph and that he was a sex offender, she started to cry," the mother said.

Authorities recommend parents monitor what their children are saying and who they are talking to on every Web site.

The mom said she did what she did for every child and hopes that other parents will do the same thing.