After the second night of unrest in the city's streets, Philadelphia officials just announced that a 9pm curfew will go into effect Wednesday evening.

All businesses in the city of Philadelphia must close at 9 pm. Residents are urged to stay inside until the curfew expires at 6 am. Essential services (grocery stores, restaurants and pharmacies) may choose to offer delivery service after 9 pm.

The curfew comes as unrest has broken out in Philadelphia both Monday and Tuesday night evenings. Businesses have been preparing for the unrest by boarding windows and closing early.

Earlier in the day, the city announced the plans for the curfew in an email sent to business owners throughout the city. Restaurants are "strongly advised" not to open for dinner service, the Inquirer reports.

The Pennsylvania National Guard has been mobilized, and they're expected to arrive in the city within the next day or so to protect critical infrastructure in the city.

Unrest Began on Monday Following Police-Involved Shooting

The unrest follows the police shooting death of Walter Wallace Jr. on Monday afternoon in the Cobb Creek section of the city.

Police say the 27-year-old ignored orders to drop a knife he was waving before officers fired their guns. A total of at least 14 shots were fired between the two officers around 3 pm on Monday, NBC 10 reports. 

Wallace's family tells the media (including CNN) that he suffered from bipolar disorder. They say he was in crisis during the time of the shooting and had called for an ambulance. They say that police knew he was in a crisis because officers had responded to the house three times earlier in the day, 6 ABC reports.

Local leaders say the incident is under investigation as they scour the evidence -- including body cam footage.

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Tensions Continue to Escalate Throughout the City

The city, meanwhile, has remained on edge since the incident.

Following Monday's shooting, hundreds gathered to peacefully protest the actions of the police. At least 500 people gathered in West Philadelphia as they chanted to demand change in the city's police reform. In fact, 30 police officers were injured as tensions escalated on Monday evening.

CNN's reporters on the scene say the situation escalated once again on Tuesday evening in West Philadelphia. In fact, police requested residents in those neighborhoods to stay indoors last night.

Looting did break out in West Philadelphia on Monday. That continued on Tuesday evening in the Port Richmond neighborhood of the city.

Television footage from CBS 3 shows people running in and out of businesses (including Target, Walmart, Dollar General, and more) along Aramingo Avenue on Tuesday evening. CNN estimates that as many as 1,000 people were involved on Tuesday evening.

The police announced that 81 people were arrested overnight Tuesday, and 23 additional law enforcement officers suffered minor injuries Tuesday evening into Wednesday morning.