Video: What Is A Holter Monitor?

2 Schools Decimated by Okla. Twister

Two-mile-wide tornado touched down just as students were being released from school.

Tornado Twists Through Okla.

Twister ripped apart homes from Newcastle to Moore, a path of 12 miles.

Hero Teacher: 'I Saw the Tornado Coming'

Sherri Bittle and Cindy Lowe helped save dozens of lives when the tornado hit Briarwood Elementary.

Massive Tornado Devastates Oklahoma City Area, Dozens Killed

Elementary schools, homes and hospitals were destroyed in the monster twister's wake.

Tornado Rips Through Moore, Okla.

The National Weather Service says tornado had wind speeds up to 200 mph.

Oklahoma Tornado Leaves Behind Mangled Heaps

The 2-mile-wide tornado reduced neighborhood blocks to smoking piles.

Storm Chasers in a Tornado Outbreak

Veteran storm chaser Ginger Zee with the latest breaking news and storm developments.

Jodi Arias to Donate Hair, Recycle If Allowed to Live

Convicted murderer says she "can't in good conscience" ask jury to sentence her to death.

Jodi Arias Judge Denies Attorneys' Request to Withdraw

Kirk Nurmi asked for a mistrial in the death penalty phase citing prosecutorial misconduct.

Oklahoma Tornado Destroys City for 2nd Time

Forty-one died in 1999 when a tornado touched down for 18 miles in the city of Moore.

Aftermath of the Oklahoma Tornado

Emergency and rescue workers rush to help survivors.

Police End Search for Missing Mom Susan Powell

Utah police say they lacked evidence to bring charges in the case of Powell's 2009 disappearance.

Florida Teen Arrested for Same-Sex Relationship

Kaitlyn Hunt, 18, faces felony charges for having a sexual relationship with a 15-year-old girl.