As soon as the mission starts, examine the Declassify mission skull to the left. For this section, you have to complete your objectives within 4:15 before the explosives detonate. You'll encounter ragers, kantus, maulers and cleavers in this section. There's some frag grenades to the left of the first area and a mulcher in an alcove past the gate of the first Courtyard.
Continue down the ramp and you'll encounter ragers. Kill them all quickly and proceed forth. Once you've reached the street, continue ahead, past the corner to find a COG tag skull on the far wall. The COG tag is located between some cars to the right. Regroup with your team to complete the section.