It is not clear what happened to Alex on the third pitch of the Pharaoh. Simply stated, it sounds like he fell, some of his gear didn't hold, and he died when his head hit the rock during the fall. One can only speculate about what happened. It goes without saying: be careful when you place gear - your life may depend on it.
The part of the story that is intriguing is the situation that Tom found himself in. He was at the top of the second pitch on a multi-pitch climb with his partner hanging on the other end of the rope. Immediately after the accident, he didn't know if Alex was alive and requiring immediate medical attention or dead. This placed an enormous amount of stress upon him. He needed to move fast to help his partner, yet he had to be incredibly careful - he was high on the wall without any support or belayer. The job he did in going to Alex's aid and later getting himself off of the wall was incredible. It is a true lesson in itself on what can occur on a multi-pitch climb.
If you climb multi-pitch climbs, the Pharaoh accident brings to light the difficult situation a belayer can find themselves in when a leader accident occurs. It is fairly common for a strong leader to take a partner along on a multi-pitch climb who can follow and belay. It may be a wife or inexperienced friend. You need to make sure that both you and your partner understand basic climbing fundamentals: how to escape the belay, how to set up a gear belay if you have to rappel, and how to transfer weight from one anchor to another. It is also important to have basic communication skills: where the keys to the car are located and where the phone is. If you aren't strong in the fundamentals, stick to the single pitch climbs.
Look at your partner and yourself. Put yourself in Alex and Tom's situation. If the leader in your party fell and was killed or injured, could the belayer successfully come to their aid or escape and get help? Think about it objectively.
A common theme amongst most climbing accidents is that the rescue begins with a phone call. The sooner you make the call, the sooner the rescue begins. In the case of the Pharaoh, it would have taken a great deal of stress off of Tom if he had a phone with him on the climb. Although I don't know this for a fact, there appears to be a straight line into town from the face of the Pharaoh. If he had had a phone with him, the rescue could have started almost immediately after the accident. (Note: having a cell phone would not have changed the ultimate outcome on the Pharaoh).
Since the Pharaoh accident, I have made it a rule to carry the cell phone with me at all times when climbing. On the face of most multi-pitch climbs, you can get good phone reception. You are up high and typically have a clear line of sight to areas of good cell phone reception. I have called into town from the top of "Papillion" in Mendoza Canyon and had good reception on the Whale Dome in Cochise Stronghold. Modern cell phones are small and powerful. Likewise, the number of cell phone antennaes are increasing daily. This means the chances of good reception are very likely in most locations.
If you are buying a cell phone, keep climbing in mind. Don't go cheap. Get a phone that you will feel comfortable keeping with you while climbing. Keep it small and powerful. The closer you keep it, the better. It is easy to strap the modern phones onto your harness and carry it along on a multi-pitch climb. Likewise, if you only take one phone along, make sure the belayer has the phone. It is most likely that the leader will be the climber who sustains the injuries.