What could this be?

[Yutyrannus]

That is certainly a cat judging by the way it walks.

[Seijun]

Here are better pictures and even video http://ktla.com/2014/08/01/norwalk-mystery-animal-is-no-mountain-lion-but-what-is-it/
It looks more lion-like here, but the short tail, and the fact that "released pet lion" incidents are virtually unheard of in the states, leads me to still suspect dog. In every instance that I know of where a non-native big cat was released or escaped, its always been found out immediately because lions and tigers never seem too keen on hiding, lol.

But they do happen. Case in point, 2002 Arkansas.

http://www.cbsnews.com/news/lion-scare-has-arkansas-town-on-edge/

It can happen, but like I said, it is extremely rare. People mistaking common dogs and cats for Big Cats is far more common.

In the Arkansas incident, it was a very rural area, yet all 4 animals were found and killed within a week. Like I said, escaped or released big cats are not very good at hiding. I would be very skeptical that in such a dense area like LA, an African lion or any other domestically raised big cat could remain hidden for so long. Unlike a wild animal, a human raised Big Cat has very little incentive to remain hidden from anyone, and would be spotted as soon as it came out to drink, sunbathe, or eat someone's pet.

[Gwangi]

It can happen, but like I said, it is extremely rare. People mistaking common dogs and cats for Big Cats is far more common.

I would hope it would be rare! Any other time I would side with you on this debate and while I am not personally convinced it is an African lion a lot of other people far more knowledgeable than I think it is. That is all I was reporting. What I do feel confident about is that this is a big cat and not a dog.

[Hynerpeton]

Yup not a dog i can agree on that.

[SpittersForEver]

In my opinion it is most defiantly an escaped animal possibly an exotic pet or maybe even a circus animal?
Speaking of exotic pets I once saw a wolf dog hybrid  on a lead in America. (well it was 85% timber wolf, 15% husky)

[Seijun]

There are a lot of wolfdogs in the states. They are awesome animals though

[Hynerpeton]

There are a lot of wolfdogs in the states. They are awesome animals though

Never heard of em. Lol

[Yutyrannus]

There are a lot of wolfdogs in the states. They are awesome animals though

Yes, they are cool!

[SpittersForEver]

Has it been caught yet?

[Gwangi]

Listened to a new Monster Talk episode that discussed this animal. Long story short, it's a dog but it's not completely our faults for thinking it was a cat. For starters, the footage we all saw was taken at half the actual speed the animal was traveling at.

Listen to it, it's only 15 minutes long and very insightful.
http://www.skeptic.com/podcasts/monstertalk/14/09/10/

[Seijun]

Well that explains a lot, lol
Here is a video comparing the two speeds.
https://www.youtube.com/watch?v=Zh2OZGa2H_8