Chicago ? A Muslim convert who talked about his desire to wage jihad against civilians was charged Friday in a plot to set off hand grenades at a shopping mall at the height of the Christmas rush, authorities said.

Investigators said Derrick Shareef, 22, an American citizen from Rockford, was acting alone and never actually obtained any grenades. He was arrested Wednesday when he met with an undercover agent in a parking lot to trade a set of stereo speakers for four hand grenades and a gun, authorities said.

“He fixed on a day of December 22nd on Friday … because it was the Friday before Christmas and thought that would be the highest concentration of shoppers that he could kill and injure,” said Robert Grant, the agent in charge of the Chicago FBI office.

Authorities said Shareef had been under investigation since September, when he told an acquaintance that “he wanted to commit acts of violent jihad against targets in the United States as well as commit other crimes.”

The acquaintance immediately informed the FBI, officials said.

Federal officials said Shareef planned to set off four hand grenades in garbage cans at the CherryVale shopping mall in Rockford, about 90 miles northwest of Chicago.

Other potential targets that Shareef allegedly discussed included government facilities such as courthouses and city hall, authorities said.

Shareef was born in the United States and converted to Islam, officials said. They believe he might have learned about jihad through videos and Web sites.

“While these are very serious charges, at no time was the public in any imminent peril,” U.S. Attorney Patrick J. Fitzgerald said in a statement.

A spiritual leader of Rockford-area Muslims commended authorities for intercepting the alleged plot and reiterated “the Muslim community’s condemnation of terrorism in the name of Islam,” said Shpendim Nadzaku, imam of the Muslim Association of Greater Rockford.