Watching over Alcatraz Island

U.S. park police officer Gregory Johnson arrives at the Alcatraz dock to begin his 18-hour shift as night watchman.  (Robert Durell / LAT)

A National Park Service worker hands the keys to the island to Johnson, right. When the last ferry boat filled with tourist left at sundown, he was alone for the night.  (Robert Durell / LAT)

Johnson patrols near the Alcatraz Island lighthouse. “Man,” he whispers, “I couldn’t imagine being out here at night without my gun.”  (Robert Durell / LAT)

During his rounds of the penetentiary, Johnson checks out the third tier of one of the cellblocks. The prison once housed the likes of Alphonse “Scarface” Capone, bank robber and gangster Arthur “Doc” Barker, and kidnapper Alvin “Creepy Karpis” Karpavicz, a former Public Enemy No.  (Robert Durell / LAT)

Johnson stands next to a mannequin modeling the traditional prison guards uniform. Three guards were killed in two incidents at Alcatraz while it was a prison.  (Robert Durell / LAT)

Johnson inspects a boiler room at the former prison. Every now and then, the old prison plays tricks on his mind. The wind howling outside often seems like crazy laughter. One night he thought he heard clinking glasses. “This is one creepy place after dark,” he said.  (Robert Durell / LAT)

Johnson’s nightly rounds of Alcatraz take him through a tunnel. Employees of the company that now runs the tourist ferry service will soon take over night watch duties.  (Robert Durell / LAT)

Johnson uses an electric cart for part of his patrols. He plays upbeat music on his iPod - Prince, Wham!, Michael Jackson - to lighten the gloom.  (Robert Durell / LAT)

Johnson patrols outside the warden’s house and main cellblock. His shift runs from 3 p.m. to 9 a.m.  (Robert Durell / LAT)

Near the end of his 18-hour shift, Johnson watches the first ferry of the day arrive at the island’s dock.  (Robert Durell / LAT)

Marking the end of his shift, Johnson gives the keys to the island to a National Park Service employee who arrived aboard the first ferry boat of the day.  (Robert Durell / LAT)