Another damning video of a D.C. Metro operator has surfaced, this one showing the driver sleeping at the controls.

The stunning footage was captured June 18 by a 14-year-old passenger on the subway's green line in Maryland, only a few days before the deadly red line crash that killed nine people and injured more than 70.

"At first he's dozing off ... he's not in a full sleep," the boy, Gregory Thomas, told FOX 5. "I see him start to doze off and his head going limp."

Click here for the video of the sleeping Metro driver and more from MyFOXDC.com.

The teen sent the video to Metro officials on June 23, the day after the fatal accident. He said it should be a wake-up call.

"They need to review their drivers and give them better training," said Thomas.

It was the second alarming video of a Metro driver to be circulated in two days.

On Wednesday, news emerged that a clip of a subway operator texting while at the controls had been posted on YouTube and the driver suspended for five days without pay.

Click here to watch the texting clip.

Metro spokesman Steven Taubenkibel praised Thomas for sending the tape and encouraged other passengers who witness anything amiss to come forward.

"We want to know exactly what's going on," Taubenkibel said. "If people see something they don't feel is safe please let us know."

It wasn't immediately clear whether the sleepy driver has been disciplined.

Taubenkibel stressed that the blue line texting infraction occurred while the trains were operating in automatic mode. Since the deadly crash, all Metro trains are being run manually.

Officials say no evidence has been found that the operator killed in the June 22 accident on the red line was texting.