DETROIT — Moments after a judge ruled that Mayor Kwame Kilpatrick could be released from jail if he pays a $50,000 bond, Michigan’s attorney general announced he was charging the mayor with two felony assault charges stemming from a confrontation between Mr. Kilpatrick and a sheriff’s detective.

The detective accused the mayor of pushing another investigator while recently trying to serve a subpoena on of Mr. Kilpatrick. The two counts of assaulting or obstructing a police officer are each punishable by up to two years in prison.

“In my almost 20 years, first as a prosecutor and now as an attorney general … I cannot recall ever seeing let alone hearing of a situation where a police officer trying to serve a subpoena was assaulted,” Attorney General Mike Cox said at a news conference.

Mr. Kilpatrick spent last night in a one-man jail cell with no TV for violating his bond in a criminal perjury case that has dogged him for months. Then Wayne County Circuit Judge Thomas Jackson altered the ruling of the lower court judge who ordered the mayor to jail.

Judge Jackson said District Judge Ronald Giles went too far by not attaching some kind of cash bond to his ruling.

In order to get out of jail, Mr. Kilpatrick must pay a $50,000 cash bond and wear an electronic tether. He won’t be allowed to travel.

Cox, meanwhile, announced the assault charges after state police wrapped up an investigation of the confrontation between Mr. Kilpatrick and a sheriff’s detective, who accused Mr. Kilpatrick of the pushing incident in July while the investigator was trying to serve a subpoena on a Kilpatrick ally and possible witness, Bobby Ferguson.

Brian White, who works for the Wayne County sheriff’s office, testified Mr. Kilpatrick came outside of a house belonging to his sister, Ayanna, and threw him into another investigator. Mr. White didn’t fall but said he may have a slight hip fracture.

White is a lead investigator in Mr. Kilpatrick’s perjury case. The mayor and a former top aide are charged with perjury, misconduct and obstruction of justice, all tied to their testimony in a civil trial last year. At the heart of that case: steamy text messages contradicting their claim that they didn’t have a romantic relationship.

To remain free while the case moves through court, Mr. Kilpatrick was required to notify authorities about business that required out-of-state travel.

He admitted violating that condition when he went to Windsor, Ontario — minutes from Detroit — on July 23 to discuss the sale of the city’s portion of a tunnel connecting America and Canada. He didn’t call prosecutors or inform the court.

Saying he wanted the mayor treated like any other defendant, Judge Giles yesterday ordered the leader of the country’s 11th-largest city jailed. Mr. Kilpatrick was transported to jail in a sheriff’s van, photographed, given a green jumpsuit, and placed in a one-man cell for high-profile people. He wore a tan suit to his court hearing this morning.

Earlier yesterday, Mr. Kilpatrick and Christine Beatty waived their right to a preliminary exam in the perjury case. That means those charges now go directly to Wayne County Circuit Court. Arraignment for the pair was set for Aug. 14. Both deny the charges.

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Associated Press writer Jeff Karoub in Detroit contributed to this report.