Anti-vaccine activists threw what appeared to be a menstrual cup full of red liquid at California lawmakers on Friday, prompting an evacuation on the final day of the legislative year. “A few minutes ago, the anti-vaxxer stalkers - who’ve engaged in a harassment campaign all week— dropped a red substance onto the Senate floor from the elevated public gallery, dousing several of my colleagues,” state Sen. Scott Wiener tweeted. “The person who committed this assault screamed it was baby blood. These anti-vaxxers are engaging in criminal behavior,” he said. Several lawmakers were reportedly splashed with the red liquid, and authorities were trying to determine what exactly it was after one of the protesters claimed it was menstrual blood. The protesters had reportedly been watching lawmakers from the public upstairs balcony when the liquid was thrown. Protesters had spent much of the day Friday railing against two bills signed into law earlier this week that will crack down on medical exemptions for childhood vaccines.