According to Giants beat reporter Andrew Baggarly, there was a bomb threat at Wrigley Field following the contest. He provided more context with a quote from a police officer and described the scene:
Carrie Muskat of MLB.com and John Shea of the San Francisco Chronicle shared pictures of the police presence around the iconic stadium, while Paul Skrbina of the Chicago Tribune passed along the reason the press was asked to leave the building:
Fortunately, the game was already over when the situation unfolded, and David Haugh of the Chicago Tribune noted that “a few officers outside said they thought players were being evacuated too, along with everybody else. Place was empty walking out.”
While the players and media were evacuated for some time, Baggarly noted that security eventually gave the "all clear at Wrigley" and pointed out "stadium workers, cleaners, media and grounds crew were allowed back inside."
The Cubs would later release a statement on the matter, via Baggarly:
As for the actual baseball at Wrigley Field, Chicago built a 3.5-game lead over the Giants in the race for the second National League wild-card spot with Sunday’s victory. Shea pointed out that at least one policeman had a good sense of humor following the victory despite the serious nature of the situation:
The Cubs have a scheduled day off Monday, and security will likely remain vigilant given Sunday’s developments.