This just in from Nextdoor Sunnyside: "There is SFPD activity at Riordan High School due to a bomb threat. According to SFPD dispatcher, some homes near Riordan and Riordan High School (175 Phelan Ave) as well have been evacuated. SFPD units are investigating. Judson at Gennessee to Phelan has been blocked off by SFMTA."
Over in Glen Park, we can hear public address system (however muffled) announcing the evacuation.
SFist will update as soon as we know more.
UPDATE: This situation has been cleared. "SFMTA has opened up Judson again, and per SFPD Dispatcher, the situation has been cleared by SFPD." Move along, folks. Nothing to see here.