It looks like the troops hit him. I'm having trouble linking stuff in the body. I'm kind of a newb at this so here is an excerpt from an MSNBC article.
"NAJAF, Iraq - Radical Shiite cleric Muqtada al-Sadr has been wounded during fighting between his followers and U.S. and Iraqi forces in the holy city of Najaf, Arab satellite television networks said Friday, quoting his aides.
Al-Sadr is said to be holed up in Najaf’s sacred compound housing the Imam Ali shrine, surrounded by his followers. He has led an uprising against coalition troops for more than a week in the city, vowing to fight “until the last drop of my blood has been spilled.”
Aide Ahmed al-Shaibany said al-Sadr was wounded in three places during the clashes, Al-Jazeera reported, but didn’t say what happened or if the wounds were serious.
Another aide, Abdel Hadi al-Daraji, told al-Arabiya television that al-Sadr was hurt during shelling."
It's good that they've finally got the guy. Let's see if he surrenders, or does indeed fight to the last drop of blood.