The first blackout happened just before the Monday Night Football matchup between the San Francisco 49ers and the Pittsburgh Steelers. The assumption was the flash of light was a transformer exploding, but it turns out that's not what happened.
The 12,000-volt power line arced near Candlestick Park. PG&E said it was a splice that connects two electrical wires that failed on a power pole, causing the line to fail. Television screens around the country went black when that happened -- unfortunate timing as it coincided with Monday Night Football.
At 5:18 p.m., a lightning-like flash of light at Candlestick Park caused the lights to go out, 20 minutes before the opening kickoff.
Tens of thousands of fans sat in the dark.
"I've been coming here for 40 years, and this is the first time," one fan said.
Another fan said friends were calling her, trying to figure out what was going on. Players on the field also wondered.
"We're sitting on the sideline and we're getting cold," 49ers tight end Vernon Davis said. "And we're trying to keep warm, and then we have to go warm up all over again."
After a while, the backup system kicked in which kept some of the lights on in the stadium. It took almost a half hour before electricians could get the field lights on.
The game resumed until the second quarter when the lights went out again.
At 6:43 p.m., the stadium went dark, bringing everything to a halt with the 49ers leading 6-0. The game resumed 16 minutes later when the lights came back on.
Mayor Ed Lee was in the stands when the lights went out. It was a sobering night for the mayor.
"This was an embarrassing situation," Lee told reporters on Tuesday. "My apologies to the National Football League, as well as to the 49ers, to their players."
Since a night game was being played, there were more police in the stadium. As it turned out, the crowd behaved themselves.
"In terms of crimes occurring at Candlestick last night, there was, in my opinion, less than normal," San Francisco Police Capt. Paul Chignell said.
At first, PG&E blamed a city-operated switch that malfunctioned. The city quickly responded.
"There's nothing to indicate that the power failure was caused by city equipment," Ed Harrington, with the San Francisco Public Utilities Commission, said.
PG&E later said the first outage was caused by a downed power line.
"There was a wire that came down last night on one of the electrical circuits that feeds the station," PG&E spokesperson Joe Molica said.
PG&E crews replaced the 12,000-volt power line overnight, but the cause of the second outage is still a mystery.
"It doesn't appear that there any electrical fault on our end, but I want to stress we're continuing to work with the city," Molica said.
Engineers from the PUC and PG&E met Tuesday afternoon to try to figure out what caused the outages. PG&E says it has no clue on what caused the second outage and it's not sure why the splice failed. Although work had been done on the line, no one can say when because there are no records and PG&E says it wasn't required to keep them.
"They indicated that it was probably performed in response to a different outage, probably an emergency repair and that's why they didn't have records on when it occurred," SFPUC Asst. General Manager Barbara Hale said.
PG&E said the records it did have indicated no problems.
"So from their perspective, it was in good working condition, but failed," Hale said.
A spokesperson for the 49ers said it was too soon to tell if the team lost any money or if fans who left might get a refund.