Update 4: 8:31PM EST, LE taking a careful approach as they want to apprehend the suspect alive.  Meanwhile, CBS is reporting that a foreign government asked the FBI to interview Tsarnaev (probably the older brother) which they did two years ago.

Update 5: 8:43PM EST, the suspect is now in custody.  It sounds like HRT made the arrest.

Update 6: Picture of the perp:

The hunt continues for the remaining suspect involved in the Boston marathon bombing, their trail of destruction leaving almost 200 wounded and four dead.  The brothers Tamerlan and Dzhokhar Tsarnaev are the alleged perpetrators behind the bombing and their motives are still being debated.

Something we’ve been thinking of since they released the background information on the two brothers was re-iterated perfectly by Peter Bergen – if they were radicalized Chechen extremists, then they should be out blowing up people in Moscow, not in the United States. Russia is the number one enemy of Chechnya, not the “far Satan” AKA the United States in al-Qaeda lingo.

It seems likely that the brothers will turn out to have personalities that are inconsistent with our preconceptions about radical Islam.  Like the 9/11 hijackers who drank alcohol and hung out at strip clubs, the Chechen brothers listened to secular non-Islamic music and even smoked marijuana.  Human beings are terribly inconsistent when it comes to ideology so this shouldn’t surprise us in the least.

While on the run last night, the brothers car jacked a vehicle and apparently forced the driver to take them around town and make ATM withdrawals in order to build up a war chest for their escape.  The circumstances are unclear but at some point in the night they made contact with law enforcement and a firefight broke out, killing Officer Sean Collier.

A chase ensued with the brothers throwing improvised grenades at the police in pursuit before they stopped the car and unloaded with semi-automatic weapons (fully automatic according to some reports but that seems in doubt when listening to the audio track in the above video). The exact details of what happened next are no doubt being investigating by Boston PD but initial reports state that one of the brothers threw a smoke grenade and then the older brother, Tamerlan, charged the police while firing at them.  The younger brother got back in the stolen Mercedes and took off, possibly running over his brother while smashing between two police vehicles, taking off doors and mirrors.

The 19-year old Dzhokhar made it a couple more blocks before abandoning the vehicle and bailing out on foot.  Blood splatter was found around the vehicle which was also pockmarked with bullets from police gunfire.  It is highly likely that Dzhokhar is injured while he is still on the lam.

It appears that attempts were made to save Tamerlan’s life by law enforcement officers after he had been shot and possibly ran over by his younger brother.  You can see in pictures that have been leaked onto the internet of the corpse that an incision was made in his side, probably to stop internal bleeding.  It was also discovered in the morgue that Tamerlan had been wearing a suicide vest all a long with an attached detonation device.  If he hadn’t been shot/run over he probably would have blown himself up once Police Officers moved in to make the arrest.

A perimeter was established in Watertown after the shoot out to catch Dzhokhar but without success.  Helicopters were called off because of low cloud cover and after searching the entire neighborhood sector by sector on foot they have not found the suspect.  He either quickly slipped out of the perimeter before it could be closed or he crawled into the Charles River, bled out, froze, or both until he died.  At this point nothing has been confirmed.

The FBI’s Hostage Rescue Team (HRT) is now involved as are US Military units, more than likely EOD although JSOC personnel could be called in with Presidential approval but that seems unnecessary in this manhunt.  The brother’s apartment was also raided where it is reported that firearms and pipebombs were found, enough that there is good reason to think that they were planning a second wave of attacks.