Hundreds of soldiers packed onto a field for a memorial service honoring the victims of last week's shooting at Fort Hood.  

The soldiers could be seen standing in front of an American flag at half-staff at Sadowski Field at the III Corps Headquarters Building. 

President Obama was in attendance for the three soldiers killed in last week's shooting at Fort Hood in Texas. Lt. General Mark Milley honored the dead at the service.

"They had different hobbies and passions, and they all had different lives, but they were united by a single desire -- the desire to serve their country and their willingness to answer their nation's call in a time of war," he said. 

Sixteen more soldiers were injured in the shooting on the sprawling Texas military base.  The shooter, Army Specialist Ivan Lopez, took his own life.  

President Obama and First Lady Michelle Obama met privately with victims' families before the memorial ceremony began. And President Obama spoke at the service. 

Obama says the nation is drawing strength from relatives of the victims of the fatal shootings last week at Fort Hood.

He says the tragedy tears at wounds that are still raw from a deadly mass shooting on the sprawling Army post five years ago.

Obama told relatives of the victims that he's there to honor their loved ones and offer whatever comfort he can.

"It was love for country that inspired these three Americans to put on the uniform and join the greatest Army that the world has ever known," the president said. 

Fort Hood was also hit by a mass shooting in 2009 when a soldier opened fire and killed a dozen people.  

General Odierno said the military must do a better job of identifying "risk factors" and treating mental health problems.  

Snipers are keeping watch over the memorial service for last week's victims at Fort Hood.  

The snipers can be seen on top of the Three Corps Headquarters Building right next to Sadowski Field where the ceremony is being held.  

It isn't known if the snipers are military or Secret Service.  

Security is also extremely tight at Fort Hood, with tall barricades blocking people from getting into the service.  

Hundreds of soldiers are standing on Sadowski Field for the event.

-- The Associated Press contributed to this report.