Mark Wahlberg prepares to film a scene at the finish line before the start of the Boston Marathon. (Gretchen Ertl/Reuters)

Excuse me, officer, but … hey, wait a minute. You’re no police officer. You’re Mark Wahlberg.

Not that Wahlberg couldn’t help someone navigate his native city, but he was dressed as a cop at the finish line early Monday morning because he is acting in “Patriots Day,” a movie about the 2013 marathon bombings.

“There’s huge pressure to get this right,” Wahlberg told the Boston Globe last month, “but we’re committed to doing that.”

[Everything you need to know about the Boston Marathon]

Director Peter Berg, the cast and crew have been filming in Weymouth, Dorchester, and Jamaica Plain in recent weeks. Wahlberg’s presence might have been a little unnerving, but shooting took place early in the morning and the elite participants don’t start until 9:32 a.m. EDT.

“We’re aspiring for real authenticity so that means filming in real locations,” Berg said. “We will always ask and we will always be transparent with what our ask is. If there’s one person who’s uncomfortable, we’re more than happy to go elsewhere.”