>> woodruff: marcia biggs reporting from lower manhattan. minder that things can change in an instant. thank you, marcia. and we're going to be updating all of you with this latest on the new york city attack and hear more about how law enforcement evaluates acts of terror at the end of the program. on capitol hill, the first of two days of hearings exploring the role of social media in the 2016 election. representatives from facebook, twitter and google faced tough questions from a senate judiciary subcommitee. nick schifrin reports. >> reporter: for the first time, social media giants came to congress to admit publicly their platforms have a political dark side. facebook general counsel colin stretch: >> the foreign interference we saw is reprehensible. >> reporter: acting twitter general counsel sean edgett: >> the abuse of our platform by sophisticated foreign actors to attempt state-sponsored manipulation of elections is a new challenge for us, and one that we are determined to meet. >> reporter: that foreign actor is russia, and faceboo

at a time. >> reporter: for the pbs newshour, i'm marcia biggs in mosul, iraq. >> sreenivasan: tune iner. "frontline's" latest film, "mosul," was on the ground filming the fight as it unfolded street-by-street and house-by- house. that's tonight on pbs. >> sreenivasan: let's turn to the continuing fallout and reaction to the harvey weinstein story. yesterday, weinstein resigned from the board of his production company following numerous revelations of sexual harassment and several allegations of assault. more than three dozen women have said weinstein harassed them. while weinstein has admitted to behaving inappropriately, he has said he did not physically assault anyone. one of those women is katherine kendall. she was a 23-year-old actress who met weinstein in 1993. she alleges that he invited her to his apartmnt in new york where, she says, he took off his clothes and asked for a massage. as other actresses began coming forward about their painful experiences, she also went public with her own story. she joins me now from los angeles. first, thanks for joining us, and i don't want t