It's the Crescent City Connection bridge which is on highway 90, I believe, going west out of town. It crosses over to Gretna in Jefferson Parish.
Not the same sheriff per this story (UPI is listed as source):
http://news.monstersandcritics.com/northamerica/article_1047143.php/Cops_trapped_survivors_in_New_Orleans
'We shut down the bridge,' Arthur Lawson, chief of the City of Gretna Police Department, confirmed to United Press International, adding that his jurisdiction had been 'a closed and secure location' since before the storm hit.
'All our people had evacuated and we locked the city down,' he said.
The bridge in question -- the Crescent City Connection -- is the major artery heading west out of New Orleans across the Mississippi River.
Lawson said that once the storm itself had passed Monday, police from Gretna City, Jefferson Parrish and the Louisiana State Crescent City Connection Police Department closed to foot traffic the three access points to the bridge closest to the West Bank of the river.