MINNEAPOLIS – A former Minnesota nurse who told police he went on the Internet and encouraged dozens of depressed people to kill themselves for the “thrill of the chase” was charged Friday with helping a Canadian woman and a British man commit suicide, authorities said.

After nearly two years of investigation, William Melchert-Dinkel, 47, was charged with two felony counts of aiding suicide under a rarely used decades-old state law that legal experts say could be difficult to prosecute on freedom-of-speech grounds.

Melchert-Dinkel, a married father of two, is accused of encouraging the suicides of Mark Drybrough, 32, who hanged himself at his home in Coventry, England, in 2005; and Nadia Kajouji, 18, of Brampton, Ontario, who drowned in 2008 in a river in Ottawa, where she was studying at Carleton University.

Prosecutors claim Melchert-Dinkel posed as a female nurse, then feigned compassion for those he met in suicide chat rooms, while offering step-by-step instructions on how to take their lives.

The criminal complaint filed in the case said he told investigators he encouraged “dozens” of people to commit suicide and “characterized it as the thrill of the chase.” He also estimated that he had actually helped five or fewer people kill themselves.

Kajouji’s mother, Deborah Chevalier, said she was overwhelmed when she heard the news. “My insides were shaking,” she wrote in an e-mail, adding that the charges were long overdue.

Melchert-Dinkel, whose first court appearance is scheduled for May 25, told police in January 2009 that he stopped the Internet chats shortly after Christmas 2008 for moral and legal reasons. He said he “felt terrible” about the advice to commit suicide he provided to others.

An e-mail found on Drybrough’s computer from Melchert-Dinkel showed him giving technical advice on how to hang yourself from a door, “you can easily hang from a door using the knob onw (on the other) side to tie the rope to, sling it over the top of the door, attach the noose or loop to yourself then step off and hang successfully,” the complaint says.

The investigation tied Melchert-Dinkel to Kajouji through searches of their computers. Canadian authorities determined she had online discussions with someone named Cami and entered into a suicide pact with her. A search of his computer revealed a photograph of Kajouji and correspondence between him and other suicidal people.

Some experts say prosecuting the state law, which carries a maximum penalty of 15 years in prison and a $30,000 fine, could be difficult because Melchert-Dinkel didn’t physically help kill them, just allegedly encouraged them and gave technical directions. The state law does not specifically address situations involving the Internet or suicides that occur out of state.