They then stayed there shouting political slogans (largely about British soldiers killing Muslims) at passersby until police finally showed up and shot both of them and took them into custody. (Both are in the hospital; one in serious condition.) This report suggests that one woman, Ingrid Loyau-Kennett - who got off a bus and then talked to the men until police showed up - may have prevented the incident from escalating or more being killed. At least a couple people videotaped what was happening. Here's the basic AP rundown with more details.
This new report says that both men had been investigated in previous security service probes for links to terror groups.
Here's some of the video I mentioned above.